How to weigh your truck and trailer

[chris]

A video we watched in truck driving school that helped us to understand weighing and distribution.


Remember that your weights have to fall in line. Front Axle, Rear Axle, and Gross Vehicle Weight for your tow vehicle. If any of those are over, then you are technically "Over Weight". But, there are a number of factors that impact all of this. There is a whole chain of capacities that impact each of these.

1. Tires - Each tire is rated for a certain amount. Simply getting "10 ply" or E rated tires doesn't cut it. Look at the rating of the tire, and look at the weight capacity of each tire. Since you have two tires on your axle, then you multiply by two. If you have a dually, you take the dually load, and multiply that by 4. When you run tires in a dual configuration with them budded together, the ratings drop. So if a tire is good in a single configuration for 3500 pounds, in a dually config, each tire may only be rated for 3100 pounds. Multiplied by 2 for a single configuration, you have 7,000 lbs capacity, or in a dually configuration, you would have 12,400 for the same tires.
2. Rims - Rims also have a weight capacity. If you're going to try to tow heavy, you should be sure that your rims are capable. If your tires are rated for 4,000 each, but your rims are only rated for 3,500 pounds, then that is your weak link and you need to make sure you do not exceed 7,000 pounds.
3. Axle - Axles are rated for a weight amount too. That may be your negating factor, and it is important to know what they are rated for.
4. Your Gross Vehicle Weight is probably not the combined total of FAWR and RAWR (Front and Rear Axle Weight Ratings). The manufacturer may consider the frame unable to carry the extra weight, so you may have 3K FAWR, and 6K RAWR, but your GVW may only be 8K lbs instead of 9K lbs due to frame restrictions.

Your weight sticker is the key. It is the certified weights that you are capable of carrying.

Let me know if you have any questions.
Chris

[Cate&Rob]

Another consideration for RV trailers and 5th wheels is side-to-side weight difference. This is caused by the appliance and storage layout of the trailer. For example, Reflection 303 and 337 5th wheels will have 800 to 1000 lbs more weight on the left (street) side tires because fridge, stove, pantry and most other storage space is on this side.

A CAT scale or similar only gives you weights for each axle and usually this includes one weight number for all trailer tires. You can't just divide the trailer number by four to get an accurate understanding of the weight being carried by each trailer tire.

There are outfits that will weigh every tire position individually, but you have to be a little critical of the data they provide. It is only as accurate as the scales they are using. At the last Indiana Rally, several participants received information indicating that the left front tire of their trailer was really heavy. The reason given was that this was the location of the fridge. Then we noticed that the truck rear tire weights that had been almost equal without the trailer became much heavier on the left side with the trailer. There is no physical way for a point load from the trailer pin on the centerline of the truck to increase the weight on one truck rear tire more than the other. It was observed that the same weigh scale was used for the left front trailer tire and the left rear truck tire. I do not know if this discrepancy was ever resolved.

Just FYI . . .

Rob

[arhayes]

Escapees SmartWeigh program weighs by wheel/axle for both the TV and the rig. Let's you know not only side to side as well as what each axle is carrying. Good info and helps you understand why the TPMS shows different temps and pressures as you're going down the road.


Alan

[SmallBoxMaker]

There are outfits that will weigh every tire position individually, but you have to be a little critical of the data they provide. It is only as accurate as the scales they are using.

You also have to be critical about how they write down the numbers. When we are the TN rally last year we had our rig weighed and the numbers they gave us showed identical left and right wheel weights, to the pound. I can only assume that this was due to carelessness in transcribing the weights from the paper copies that they made during the weighing.

[Cate&Rob]

If you are planning to have individual wheel weighing done at a Rally, I would suggest that you arrive with a recent CAT Scale printout so that you have a reference to "discuss" with those doing the individual wheel weighing. If their weights do not sum to the CAT Scale totals by axle, I would certainly challenge their data. I watched their process a couple of years ago and chose not to invest in getting them to weigh my rig. Just my personal choice.

Rob

[Paul & Deb]

If you are planning to have individual wheel weighing done at a Rally, I would suggest that you arrive with a recent CAT Scale printout so that you have a reference to "discuss" with those doing the individual wheel weighing. If their weights do not sum to the CAT Scale totals by axle, I would certainly challenge their data. I watched their process a couple of years ago and chose not to invest in getting them to weigh my rig. Just my personal choice.

Rob

Good point Rob. I got ours weighed at the rally last year and have essentially disregarded their results. The numbers did not add up "to me" plus the people doing the work we're, in my opinion, well, I shouldn't call people names. I will say they were totally unprofessional. They were complaining and literally throwing the scales around to the point that I have no confidence that they were in calibration.

Hopefully the crew coming in this year will be different and much more professional!

[arhayes]

In my case I had it done in Livingston at the Escapees headquarters. I'd previously CAT weighed and their per axle numbers were not significantly different. Total rig and rig + TV were spot on. YMMV


Alan